Telecommunication networks provide subscribers with various telecommunication services for which a network operator or a service provider bills the subscriber to a service or the user of a network connection. The most common telecommunication service is a speech call or a data call, for which the user is charged based on the duration of a call, for example, according to a given call tariff. Conventionally, call charges over a certain billing period are collected together and the subscriber or the owner of the network connections is billed afterwards. However, tariffs and charges for mobile calls, international calls and various special services may be quite high, which may result in unexpectedly high call charges over a billing period. In order to avoid unpleasant surprises, some subscribers wish to set a maximum limit to charges for calls made during a given period by themselves, members of their family or their employees. This can be implemented such that, for example, when the accumulated charges of a certain subscriber or subscriber group reach a given limit, the subscriber is prevented from using the network or services, and thus causing more charges.
In some telecommunication systems, the subscriber may prepay all his or her telecommunication services. In such a case, the subscriber can use the services only if he or she has a positive prepaid balance; when the prepaid balance becomes zero or when it is too low for the requested service, no service will be provided. In the present application, subscribers who are charged based on prepayment or a certain credit limit are called balance-limited subscribers. Balance limits are set by using contracts between the subscriber (or the owner of the connection) and the network operator or service provider through the service point of the network operator. If, for example, those who are responsible for the expenditures (e.g. parents) have provided other subscribers (e.g. children) with a certain prepaid balance per month and the balance has been exhausted before the proper time and those who are responsible have wished to increase available operation time (to enable a child to make calls after the previously agreed balance is overdrawn), they have been compelled to carry out this function through the service point of the network operator, which has not only been difficult for the subscriber but also required administrative work from the operator, thus causing delay.